Q: I leave my
perennials standing through winter for several reasons, one of which is to
preserve a place for beneficial insect eggs. For many plants, like sedum, I
always heard to remove the old growth after
new growth starts in spring. But what happens when new growth starts when
it's still too cold for the insects to have hatched?

How
late into the spring do I have to wait to remove last year's remains to
maximize beneficial insect development? No point looking at old stems all
winter only to remove them too soon in the spring and lose the insect
benefit.

If
I cut the old perennials down now and put the material on the compost pile,
will the eggs still hatch?

A: That's a really
excellent, practical question and one that I've never seen written about much.

It
does pose a dilemma between getting the yard looking reasonably good and ready
for a new season vs. wiping out the beneficial-insect population at the last
minute.

Different
species (mantids, parasitic wasps, hover flies, ground beetles, spiders, etc.)
emerge at different times, but pretty much everything is up and around by May.
A majority of bugs are active most Aprils (although we're running behind so far
this year).

So
one strategy is delaying as long as possible to do your cleanup. The down sides
are 1.) it gets harder to remove old, browned-out stuff when the new stuff is
intermingling, and 2.) the old stuff detracts from the beauty of the fresh,
emerging growth.

One
compromise is to inspect your old growth as you remove it. Look for things like
chrysalises, spider egg sacs, mantid cases and such. The more you're familiar
with what these look like, the better.

A
beneficial-insect guide or Internet search can help with that. One of my
favorite bug-ID sites is BugGuide.net.

If
you notice the sacs and cases are empty, you're good to go. If not, look for a
place where you can temporarily store the cut stems until hatch.

Do
you have a wooded area nearby, for example? How about an out-of-the-way corner
where you can make a shallow pile? Or maybe you can tuck some of it underneath
trees and shrubs?

Otherwise,
place stems with unhatched sacs and cases on the top of your compost pile.

What
you don't want to do is bury egg-laden material so deep anywhere that you'll
impede hatch or start to cook it from early composting.

If
you can keep unhatched beneficials close to the surface somewhere until at
least May – even if not in its original attached position – you'll preserve the
bulk of the hatch.